CA1247345A - Wound dressing material - Google Patents
Wound dressing materialInfo
- Publication number
- CA1247345A CA1247345A CA000445917A CA445917A CA1247345A CA 1247345 A CA1247345 A CA 1247345A CA 000445917 A CA000445917 A CA 000445917A CA 445917 A CA445917 A CA 445917A CA 1247345 A CA1247345 A CA 1247345A
- Authority
- CA
- Canada
- Prior art keywords
- dressing material
- wound
- wound dressing
- mix
- region
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Materials For Medical Uses (AREA)
Abstract
ABSTRACT
WOUND DRESSING MATERIAL
A wound dressing material comprising a sheet of a synthetic plastics material which is permeable to water vapour and to air, having on one side a surface for application to a wound, and immediately behind the said surface a cellular region having a structure of collapsed, open cells which intercommunicate with one another, and a more dense region behind the cellular region, and an intermediate region in which there is a gradual transition from the cellular region to the more dense region, so that on contact with liquid exudate from a wound, the dressing material will absorb a limited amount of exudate into the cellular region but prevent it from passing right through the dressing material.
WOUND DRESSING MATERIAL
A wound dressing material comprising a sheet of a synthetic plastics material which is permeable to water vapour and to air, having on one side a surface for application to a wound, and immediately behind the said surface a cellular region having a structure of collapsed, open cells which intercommunicate with one another, and a more dense region behind the cellular region, and an intermediate region in which there is a gradual transition from the cellular region to the more dense region, so that on contact with liquid exudate from a wound, the dressing material will absorb a limited amount of exudate into the cellular region but prevent it from passing right through the dressing material.
Description
3~5 ~IOUND DRESSIt~(i PIATERIAL
This invention relates to wound dressing materials, and more specifically to a material which can be applied to many types of injury or wound but is particularly useful as a temporary ~ound cover in the therapeutic treatment of burns, varico,e ulcers, pressure areas and other related injuries. The term "burns" covers thermal, chemical, electrical and similarly inflicted wounds involving skin damaye or destruction.
Burns require a unique combination of therapy and dressing when the function of the skin is absent or impaired, because nutritious body fluids and their essential components are continuously lost through the wound, which in the case of a large area burn can cause dehydration of t'ne pa~ien~ and in turn involve more serious complications such as lung and kidney malfunctions, while the nor~al protection provided by the skin from invading harmful bacteria and other toxic and noxious agents is no longer available.
Many types of dressing material having been used heretofore. Absorbent fibrous materials such as cotton gauze can cause excessive dehydration and drying of the wound and thus become firmly adhered to the affected area, so that dressing changes are painful and can cause further damage to the wound. The natural healing process in which skin cells multiply and migrate across the moist wound surface is delayed, because the cells have to burrow deep under the dried area. Individual fibres can alss become detached from the dressing and embedded in the wound and ~hereby impede healing.
To prevent adherence and maintain a moist wound environment, dressing materials impregnated with greasy substances such as petroleum jelly have been employed. These dressings require frequent changing to avoid drying out, with consequent frequent exposure of the wound to airborne bacteria, and the greasy substances provide a good environment for the proliferation of bacteria so that wound infection is difficult to avoid, ' ' `~
~2~
while the greasy substances can also be absorbed into the wound and retard healing by ac~ing as foreign bodies.
Dressings made of polyethylene, polypropylene and polyamide films eliminate adherence of the dressing to the wound and prevent particles being embedded therein, but being non-porous they cannot absorb the excess of liquid exudate which exudes from a burn and they can therefore become painful to the patient unless changed frequently, with consequent exposure of the wound to airborne bacteria. The micro-climate under such film dressings, while favourable for healing, is also ideal for such bacteria so that wound infection again becomes a problem, while the fact that the condition of the wound is visible through the film dressing is depressing to the patient. Other film dressing materials made of gelatins, alginates and celluloses have been des;gned to create the same favourable micro-climate in the wound by dissolving or melting in the exudate and re-forming as part of the eschar (scab). This increases wound dehydration and the films, when mixed with the exudate in the eschar, become supportive of bacteria but cannot be removed from th~ wound because they have become an inteyral part of it. Even if infection is avoided, the dehydration effect delays healing. Plastic spray-on dressings involve similar problems, particularly encapsulation of dressing material deep in the wound.
Absorbent dressings of polyvinyl alcohol sponge and of polyurethane foam with an open cell structure have been found to cause wound dehydration and adherence of the dressing to the wound, while small particles of the cells of the dressing material can become detached and embedded in the wound, causing undesirable reactions. Also, passage of the exudate right through the dressing can provide a nutrient path for airborne bacteria back through the dressing into the wound. A
polyurethane foam dressing with an impermeable backing of polytetra-fluoroethylene avoids the latter problem but still suffers from theproblem of detached particles.
Biological wound covers, mainly of porcine and cadaver skin, perform ~2~
well in many respects but suffer from the problem that it is extremely difficult to avoid leaving small fragments of dermis in the wound when removing the dressing, producing subsequent foreign body reactions which can cause rejection of autografts and later breakdown of healed wounds, and causing production of antibodies which might involve serious consequences at a later date.
In British Patent ~o. 1562244 I have described a wound dressing material which is free from the disadvantages of the known materials described above, and which comprises a sheet of a synthetic plastics material which is permeable to water vapour and to air3 having on one side a smooth glazed surface for application to a wound, a cellular region behind the smooth surface, the cells in the cellular region being closed cells, and a more dense region behind the other surface~
so that on contact with liquid exudate from a wound the dressing material will absorb a limited amount of exudate but prevent it from passing right through the dressing material.
The fact that the dressing material is water vapour- and air-permeable, but will not permit the liquid exudate to pass through it, assists in maintaining a moist micro-climate favourable for healing in the wound. The smooth glazed surface avoids the danger of detachment of cell particles and assists in preventing adherence of the dressing to the wound. The cellular region enables the dressing to absorb excess of liquid exudate without drawing out so Much exudate that the wound would become dried and the patient dehydra~ed. Dressings need not be changed too frequently.
Although this wsund dressing material is very successful and is a substantial improvement over the kno~n materials described above, in certain circumstances it has a slight disadvantage in that it is not ! sufficiently pliable to conform closely to the ~ound area to be protected and has to be maintained in position by application of additional dressings and/or adhesive tapes.
~7~
I have now found an alternative wound dressing material which provides all the advantages of my earlier wound dressing material, and which is, in addition, exceedingly pliable and therefore will readily conform to the surface of a wound to be dressed.
Accordingly the present invention provides a wound dressing material comprising a sheet of a synthetic plastics ma~erial which is permeable to water vapour and to air, having on one side a surface for applica~ion to a wound, and immediately behind the said surface a cellular region having a structure of collapsed, open cells which intercommunicate with one another, and a more dense region behind the cellular region, and an intermediate region in which there is a gradual transition from the cellular region to the more dense region, so that - on contact with liquid exudate from a wound, the dressing material will absorb a limited amount of exudate into the cellular region but prevent it from passing right through the dressing material.
The physical structure of a wound dressing material in accordance with the present invention is illustrated in the accompanying drawing which shows a photograph of a transverse cross-section of a material in accordance with the invention magnified 85 times.
Preferably the synthe~ic plas~ics material is a polyurethane, in particular the product of polymerisation of a polyoxyethylene polyol with a polyisocyanate in the presence of a cross-linking agent or catalyst which is reactive with the isocyanate groups, the polymerisation being performed without any substantial amount of water present.
The preferred catalyst is dimethylethanolamine. The cross-linking agent preferably contains in its molecule two or more amine and/or hydroxyl groups which are reactive wi~h the isocyanate groups.
In a preferred embodiment, the polyol is a polyoxyethylene diol having a weight average molecular weight of approximately 3000. In a ~ Z~7~
~ 5 particularly preferred embodiment the wound dressiny material is prepared from a formulation comprising the following composition by weight;
Polyoxyethylene glycol (m.wt. 3000) lU0 parts Dimethylethanolamine 0.1-1.0 parts Silicone oil 1-10 par~s Toluene di-isocyanate 25-50 parts The invention also comprehends a method of making a wound dressing material, comprising the steps of mixing a polyoxyethylene polyol with a polyisocyana~e and, if desired, a surfac~ant with agitation to form i an aerated creamy mix, incorporating a cross-linking agent or catalyst in the mix, spreading the mix on to a smooth glazed release paper to form a sheet of a predetermined uniform thickness, and allowing the mix to polymerise at a temperature not higher than 25C, preferably below 10 C, with the exclusion of any substantial amount of water from the mix during the said steps. Preferably the release paper is supported on a flat surface, such as a sheet of glass, during the spreading and polymerising steps. The spreading may be effected by means of at least one spreader bar with a corrugated surface which is drawn over the surface of the paper at a fixed distance above it. The curing is preferably effected in a curing cabinet in which a forced draught of refrigera~ed, anhydrous air is passed over the upper surface of the sheet.
The present invention will now be illustrated by the Sollo~ing Examples.
In a preferred embodiment of the invention, the dressing material is formed by polymerisation of a polyethyleneglycol supplied by Union Carbide under the Trade Name NYAX, and having an average molecular weight of approximately 3000, with a toluene di-isocyanate supplied by Lankro Chemicals and having an Index of 109.
. .
~L~ 3~
Thus ~00 parts by weight of ~YAX polyol are mixed with 1-1~ parts by weight, preferably ~ parts by weight, of silicone oil (L-~2~; supplied by Union Carbide) to form an aerated creamy mix at a temperature of 22-25C. Subsequently, 25-50 parts by weight, preferably ~ parts by weight, of toluene di-isocyanate haviny an Index of 1~9 (supplied by Lankro Chemicals~, are blended into the mix to form a cream. Then, 0.1 - 1.0, preferably 9.5 parts, of dimethylethanolamine (sold as Propamine A by Lankro Chemicals) is mixed into the blended mix as quickly as possible.
The creamed mixture is then poured on to a smooth glazed release paper which is tightly stretched over a long table having a flat surface, such as a sheet of smooth plate glass, to ensure absence of wrinkles, folds, or ridges. The creamy mix is then spread over the paper to form a layer of uniform thickness, usually 0.5 mm thick.
The coated paper is then placed on trays which are transferred to a curing cabinet through which a current of dry, cooled air is circulated while curing of the mix takes place.
The mixing and polymerisation processes are performed in conditions which are as anhydrous as possible. Thus, the mixiny of the reactants is performed in conditions of minimum relative humidity and the air passing into the curing cabinet is dried by passing it through silica gel. The temperature in the curing cabinet is preferably maintained below lO~C, or even lower by refrigerating the air ~hich enters into the curing cabinet.
Under these conditions it is found that the volume of the creamy mix begins to increase about five minutes after the catalyst Propamine A
has been added. As the mix cures it continues to rise for about a further 30 minutes to 1 hour. Thereafter, the layer begins to "defla~e" and after a further 3 hours it has fallen to a level comparable with its ori3inal thickness.
~ fLY~3 EXA~PLE 2 A wound dressing material in accordance with the present invention is prepared in the same manner as described in Example 1 and using the same formulation as described in Example 1 but incorporating additionally the following ingredients.-Stannous octoate (supplied by Durham Raw 1 - 1~ parts by weight Materials under the Trade Namepreferably 4 parts by weiyht NEVOCURE) Trichlorofluoromethane5 - 20 parts by weight, preferably 9 parts by weight It is believed that the process used to prepare the wound dressing material of the present invention causes the initial formation of a "foamed" region in the layer of polymerising materials, which foamed region consists of open cells which communicate with one another. On completion of curing, a non-rigid structure is obtained which "collapses" as air escapes from the intercommunicating cells through the outer surface of the cured polymer.
Curiny and subsequent "collapse" of the material is usually completed in approximately four hours. The dressing material, still with its release paper backing, is cut into the required shapes and sizes for a medical/surgical wound cover by means of a band knife or roller press and is wrapped in a siliconised tissue and packaged in foil pouches which are sealed and gamma-irradiated to ensure sterile conditions.
A typical transverse cross-section of a sheet of wound dressing - material in accordance with the present invention is illustrated in the / accompanying drawing which is a photograph of ~5 times magnification.
The photograph shows a first region A of the collapsed, open cells which intercommunicate with one another, and the more dense region C
behind the cellular region, with an intermediate region B in which there is a gradual transition from the cellular region A to the more dense region C. In use, the lower surface of cellular region A as ~ 73 illustrated is applied to the ~ound to be healed.
Tests have shown tha~ the polymerized dressing material is free from ~oxic cyanate or amin~ residues and is highly effective as a wound cover in the treatment of burns. On application to a burn, it conforms to the contour of the wound and absorbs a limited amount of the liquid exudate, while swelling slightly. I~ i 5 believed that this swelling on contac~ with liquid causes the cells to open to receive liquid.
In addi~ion to the advantages mentioned above, the dressing matPrial has the specific advantages of resembling skin in texture, of conforming eas;ly and readily to any anatomical contour, and of causing no pain in application. It also has thermal insulation qualities whicn enable it to maintain an optimum temperature in the wound to promote healing. It is permea~le to water vapour and air, so as to permit the passage of gases through it, but being impermeable to liquids it prevents drying and dehydration in or around the wound area. It is non-adherent to wounds, making for painless dressing changes. It does not distort or impede X-ray examination. It is unaffected by contact with antiseptics, and under slight pressure it can act as a haemostat. It will not support bacterial life or growth and it produces no loose fibres or particles which could become embedded or encapsulated in a wound. It requires no soaking before use as with bilogical wound covers, thus saving valuable nursing time, and it can be applied by any trained nurse without specialised training. The risk of infec~ion is reduced because of the relatively infrequent dressing changes required, and the similarity of skin in texture has a good psychological effect on the patient. The production of a correct micro-clima~e in the wound increases the speed of healing.
This invention relates to wound dressing materials, and more specifically to a material which can be applied to many types of injury or wound but is particularly useful as a temporary ~ound cover in the therapeutic treatment of burns, varico,e ulcers, pressure areas and other related injuries. The term "burns" covers thermal, chemical, electrical and similarly inflicted wounds involving skin damaye or destruction.
Burns require a unique combination of therapy and dressing when the function of the skin is absent or impaired, because nutritious body fluids and their essential components are continuously lost through the wound, which in the case of a large area burn can cause dehydration of t'ne pa~ien~ and in turn involve more serious complications such as lung and kidney malfunctions, while the nor~al protection provided by the skin from invading harmful bacteria and other toxic and noxious agents is no longer available.
Many types of dressing material having been used heretofore. Absorbent fibrous materials such as cotton gauze can cause excessive dehydration and drying of the wound and thus become firmly adhered to the affected area, so that dressing changes are painful and can cause further damage to the wound. The natural healing process in which skin cells multiply and migrate across the moist wound surface is delayed, because the cells have to burrow deep under the dried area. Individual fibres can alss become detached from the dressing and embedded in the wound and ~hereby impede healing.
To prevent adherence and maintain a moist wound environment, dressing materials impregnated with greasy substances such as petroleum jelly have been employed. These dressings require frequent changing to avoid drying out, with consequent frequent exposure of the wound to airborne bacteria, and the greasy substances provide a good environment for the proliferation of bacteria so that wound infection is difficult to avoid, ' ' `~
~2~
while the greasy substances can also be absorbed into the wound and retard healing by ac~ing as foreign bodies.
Dressings made of polyethylene, polypropylene and polyamide films eliminate adherence of the dressing to the wound and prevent particles being embedded therein, but being non-porous they cannot absorb the excess of liquid exudate which exudes from a burn and they can therefore become painful to the patient unless changed frequently, with consequent exposure of the wound to airborne bacteria. The micro-climate under such film dressings, while favourable for healing, is also ideal for such bacteria so that wound infection again becomes a problem, while the fact that the condition of the wound is visible through the film dressing is depressing to the patient. Other film dressing materials made of gelatins, alginates and celluloses have been des;gned to create the same favourable micro-climate in the wound by dissolving or melting in the exudate and re-forming as part of the eschar (scab). This increases wound dehydration and the films, when mixed with the exudate in the eschar, become supportive of bacteria but cannot be removed from th~ wound because they have become an inteyral part of it. Even if infection is avoided, the dehydration effect delays healing. Plastic spray-on dressings involve similar problems, particularly encapsulation of dressing material deep in the wound.
Absorbent dressings of polyvinyl alcohol sponge and of polyurethane foam with an open cell structure have been found to cause wound dehydration and adherence of the dressing to the wound, while small particles of the cells of the dressing material can become detached and embedded in the wound, causing undesirable reactions. Also, passage of the exudate right through the dressing can provide a nutrient path for airborne bacteria back through the dressing into the wound. A
polyurethane foam dressing with an impermeable backing of polytetra-fluoroethylene avoids the latter problem but still suffers from theproblem of detached particles.
Biological wound covers, mainly of porcine and cadaver skin, perform ~2~
well in many respects but suffer from the problem that it is extremely difficult to avoid leaving small fragments of dermis in the wound when removing the dressing, producing subsequent foreign body reactions which can cause rejection of autografts and later breakdown of healed wounds, and causing production of antibodies which might involve serious consequences at a later date.
In British Patent ~o. 1562244 I have described a wound dressing material which is free from the disadvantages of the known materials described above, and which comprises a sheet of a synthetic plastics material which is permeable to water vapour and to air3 having on one side a smooth glazed surface for application to a wound, a cellular region behind the smooth surface, the cells in the cellular region being closed cells, and a more dense region behind the other surface~
so that on contact with liquid exudate from a wound the dressing material will absorb a limited amount of exudate but prevent it from passing right through the dressing material.
The fact that the dressing material is water vapour- and air-permeable, but will not permit the liquid exudate to pass through it, assists in maintaining a moist micro-climate favourable for healing in the wound. The smooth glazed surface avoids the danger of detachment of cell particles and assists in preventing adherence of the dressing to the wound. The cellular region enables the dressing to absorb excess of liquid exudate without drawing out so Much exudate that the wound would become dried and the patient dehydra~ed. Dressings need not be changed too frequently.
Although this wsund dressing material is very successful and is a substantial improvement over the kno~n materials described above, in certain circumstances it has a slight disadvantage in that it is not ! sufficiently pliable to conform closely to the ~ound area to be protected and has to be maintained in position by application of additional dressings and/or adhesive tapes.
~7~
I have now found an alternative wound dressing material which provides all the advantages of my earlier wound dressing material, and which is, in addition, exceedingly pliable and therefore will readily conform to the surface of a wound to be dressed.
Accordingly the present invention provides a wound dressing material comprising a sheet of a synthetic plastics ma~erial which is permeable to water vapour and to air, having on one side a surface for applica~ion to a wound, and immediately behind the said surface a cellular region having a structure of collapsed, open cells which intercommunicate with one another, and a more dense region behind the cellular region, and an intermediate region in which there is a gradual transition from the cellular region to the more dense region, so that - on contact with liquid exudate from a wound, the dressing material will absorb a limited amount of exudate into the cellular region but prevent it from passing right through the dressing material.
The physical structure of a wound dressing material in accordance with the present invention is illustrated in the accompanying drawing which shows a photograph of a transverse cross-section of a material in accordance with the invention magnified 85 times.
Preferably the synthe~ic plas~ics material is a polyurethane, in particular the product of polymerisation of a polyoxyethylene polyol with a polyisocyanate in the presence of a cross-linking agent or catalyst which is reactive with the isocyanate groups, the polymerisation being performed without any substantial amount of water present.
The preferred catalyst is dimethylethanolamine. The cross-linking agent preferably contains in its molecule two or more amine and/or hydroxyl groups which are reactive wi~h the isocyanate groups.
In a preferred embodiment, the polyol is a polyoxyethylene diol having a weight average molecular weight of approximately 3000. In a ~ Z~7~
~ 5 particularly preferred embodiment the wound dressiny material is prepared from a formulation comprising the following composition by weight;
Polyoxyethylene glycol (m.wt. 3000) lU0 parts Dimethylethanolamine 0.1-1.0 parts Silicone oil 1-10 par~s Toluene di-isocyanate 25-50 parts The invention also comprehends a method of making a wound dressing material, comprising the steps of mixing a polyoxyethylene polyol with a polyisocyana~e and, if desired, a surfac~ant with agitation to form i an aerated creamy mix, incorporating a cross-linking agent or catalyst in the mix, spreading the mix on to a smooth glazed release paper to form a sheet of a predetermined uniform thickness, and allowing the mix to polymerise at a temperature not higher than 25C, preferably below 10 C, with the exclusion of any substantial amount of water from the mix during the said steps. Preferably the release paper is supported on a flat surface, such as a sheet of glass, during the spreading and polymerising steps. The spreading may be effected by means of at least one spreader bar with a corrugated surface which is drawn over the surface of the paper at a fixed distance above it. The curing is preferably effected in a curing cabinet in which a forced draught of refrigera~ed, anhydrous air is passed over the upper surface of the sheet.
The present invention will now be illustrated by the Sollo~ing Examples.
In a preferred embodiment of the invention, the dressing material is formed by polymerisation of a polyethyleneglycol supplied by Union Carbide under the Trade Name NYAX, and having an average molecular weight of approximately 3000, with a toluene di-isocyanate supplied by Lankro Chemicals and having an Index of 109.
. .
~L~ 3~
Thus ~00 parts by weight of ~YAX polyol are mixed with 1-1~ parts by weight, preferably ~ parts by weight, of silicone oil (L-~2~; supplied by Union Carbide) to form an aerated creamy mix at a temperature of 22-25C. Subsequently, 25-50 parts by weight, preferably ~ parts by weight, of toluene di-isocyanate haviny an Index of 1~9 (supplied by Lankro Chemicals~, are blended into the mix to form a cream. Then, 0.1 - 1.0, preferably 9.5 parts, of dimethylethanolamine (sold as Propamine A by Lankro Chemicals) is mixed into the blended mix as quickly as possible.
The creamed mixture is then poured on to a smooth glazed release paper which is tightly stretched over a long table having a flat surface, such as a sheet of smooth plate glass, to ensure absence of wrinkles, folds, or ridges. The creamy mix is then spread over the paper to form a layer of uniform thickness, usually 0.5 mm thick.
The coated paper is then placed on trays which are transferred to a curing cabinet through which a current of dry, cooled air is circulated while curing of the mix takes place.
The mixing and polymerisation processes are performed in conditions which are as anhydrous as possible. Thus, the mixiny of the reactants is performed in conditions of minimum relative humidity and the air passing into the curing cabinet is dried by passing it through silica gel. The temperature in the curing cabinet is preferably maintained below lO~C, or even lower by refrigerating the air ~hich enters into the curing cabinet.
Under these conditions it is found that the volume of the creamy mix begins to increase about five minutes after the catalyst Propamine A
has been added. As the mix cures it continues to rise for about a further 30 minutes to 1 hour. Thereafter, the layer begins to "defla~e" and after a further 3 hours it has fallen to a level comparable with its ori3inal thickness.
~ fLY~3 EXA~PLE 2 A wound dressing material in accordance with the present invention is prepared in the same manner as described in Example 1 and using the same formulation as described in Example 1 but incorporating additionally the following ingredients.-Stannous octoate (supplied by Durham Raw 1 - 1~ parts by weight Materials under the Trade Namepreferably 4 parts by weiyht NEVOCURE) Trichlorofluoromethane5 - 20 parts by weight, preferably 9 parts by weight It is believed that the process used to prepare the wound dressing material of the present invention causes the initial formation of a "foamed" region in the layer of polymerising materials, which foamed region consists of open cells which communicate with one another. On completion of curing, a non-rigid structure is obtained which "collapses" as air escapes from the intercommunicating cells through the outer surface of the cured polymer.
Curiny and subsequent "collapse" of the material is usually completed in approximately four hours. The dressing material, still with its release paper backing, is cut into the required shapes and sizes for a medical/surgical wound cover by means of a band knife or roller press and is wrapped in a siliconised tissue and packaged in foil pouches which are sealed and gamma-irradiated to ensure sterile conditions.
A typical transverse cross-section of a sheet of wound dressing - material in accordance with the present invention is illustrated in the / accompanying drawing which is a photograph of ~5 times magnification.
The photograph shows a first region A of the collapsed, open cells which intercommunicate with one another, and the more dense region C
behind the cellular region, with an intermediate region B in which there is a gradual transition from the cellular region A to the more dense region C. In use, the lower surface of cellular region A as ~ 73 illustrated is applied to the ~ound to be healed.
Tests have shown tha~ the polymerized dressing material is free from ~oxic cyanate or amin~ residues and is highly effective as a wound cover in the treatment of burns. On application to a burn, it conforms to the contour of the wound and absorbs a limited amount of the liquid exudate, while swelling slightly. I~ i 5 believed that this swelling on contac~ with liquid causes the cells to open to receive liquid.
In addi~ion to the advantages mentioned above, the dressing matPrial has the specific advantages of resembling skin in texture, of conforming eas;ly and readily to any anatomical contour, and of causing no pain in application. It also has thermal insulation qualities whicn enable it to maintain an optimum temperature in the wound to promote healing. It is permea~le to water vapour and air, so as to permit the passage of gases through it, but being impermeable to liquids it prevents drying and dehydration in or around the wound area. It is non-adherent to wounds, making for painless dressing changes. It does not distort or impede X-ray examination. It is unaffected by contact with antiseptics, and under slight pressure it can act as a haemostat. It will not support bacterial life or growth and it produces no loose fibres or particles which could become embedded or encapsulated in a wound. It requires no soaking before use as with bilogical wound covers, thus saving valuable nursing time, and it can be applied by any trained nurse without specialised training. The risk of infec~ion is reduced because of the relatively infrequent dressing changes required, and the similarity of skin in texture has a good psychological effect on the patient. The production of a correct micro-clima~e in the wound increases the speed of healing.
Claims (15)
1. A wound dressing material comprising a sheet of a synthetic plastics material which is permeable to water vapour and to air, having on one side a surface for application to a wound, and immediately behind the said surface a cellular region having a structure of collapsed, open cells which intercommunicate with one another, and a more dense region behind the cellular region, and an intermediate region in which there is a gradual transition from the cellular region to the more dense region, so that on contact with liquid exudate from a wound, the dressing material will absorb a limited amount of exudate into the cellular region but prevent it from passing right through the dressing material.
2. A wound dressing material according to Claim 1, wherein the synthetic plastics material is polyurethane.
3. A wound dressing material according to Claim 2, wherein the synthetic plastics material is the product of polymerisation of a polyoxyethylene polyol with a polyisocyanate in the presence of a cross-linking agent or catalyst which is reactive with the isocyanate groups, without any substantial amount of water present.
4. A wound dressing material according to Claim 3, wherein the cross-linking agent or catalyst contains in its molecule two or more amine and/or hydroxyl groups which are reactive with the isocyanate groups.
5. A wound dressing material according to Claim 3, wherein the catalyst is dimethylethanolamine.
6. A wound dressing material according to Claim 3, wherein the polyol is a polyoxyethylene glycol having a weight average molecular weight of approximately 3000.
7. A wound dressing material according to Claim 3, wherein the polyisocyanate is toluene di-isocyanate.
8. A wound dressing material according to Claim 1, and which has been prepared from a formulation comprising the following composition by weight:-Polyoxyethylene glycol (m.wt 3500) 100 parts Dimethylethanolamine 0.1-1.0 parts Silicone oil 1-10 parts Toluene di-isocyanate 25-50 parts
9. A method of making a wound dressing material, comprising the steps of mixing a polyoxyethylene polyol with a polyisocyanate and, if desired, a surfactant with agitation to form an aerated creamy mix, incorporating a catalyst which is reactive with the isocyanate groups or a cross-linking agent in the mix, spreading the mix on to a smooth glazed release paper to form a sheet of a predetermined uniform thickness, and allowing the mix to polymerise at a temperature not higher than 25°C, with the exclusion of any substantial amount of water from the mix during the said steps.
10. A method according to Claim 9, wherein the release paper is supported on a flat surface during the spreading and polymerisation steps.
11. A method according to Claim 10, wherein the flat surface is provided by a sheet of glass.
12. A method according to Claim 9, wherein the spreading is effected by means of at least one spreader bar which is drawn over the surface of the paper at a fixed distance above it.
13. A method according to Claim 9, wherein the polyoxyethylene polyol is a polyoxyethylene glycol having a weight average molecular weight of about 3000.
14. A method according to Claim 9, wherein the polyisocyanate is toluene di-isocyanate.
15. A method according to Claim 9, wherein the mix is allowed to polymerise at a temperature below 10°C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000445917A CA1247345A (en) | 1984-01-24 | 1984-01-24 | Wound dressing material |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000445917A CA1247345A (en) | 1984-01-24 | 1984-01-24 | Wound dressing material |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1247345A true CA1247345A (en) | 1988-12-28 |
Family
ID=4127011
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000445917A Expired CA1247345A (en) | 1984-01-24 | 1984-01-24 | Wound dressing material |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1247345A (en) |
-
1984
- 1984-01-24 CA CA000445917A patent/CA1247345A/en not_active Expired
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4233969A (en) | Wound dressing materials | |
| US4625720A (en) | Wound dressing material | |
| US3975567A (en) | Surgical dressings | |
| US3978266A (en) | Surgical dressings | |
| US5423736A (en) | Wound dressing with dehydrated hydrogel gauze | |
| US5409472A (en) | Adhesive polymeric foam dressings | |
| US5843060A (en) | Non-adherent nasal, sinus and otic packing and method for processing sponge materials in fabrication of packings | |
| EP0300620B1 (en) | Surgical dressing | |
| US5916928A (en) | Polymer-based porous foam | |
| US5762620A (en) | Wound dressing containing a partially dehydrated hydrogel | |
| US5478308A (en) | Wound packing and package therefor | |
| US5204110A (en) | High absorbency hydrogel wound dressing | |
| AU661470B2 (en) | Wound dressings | |
| US3692023A (en) | Formable orthopedic cast materials, resultant casts and method | |
| EP0486522B1 (en) | Adhesive dressings | |
| US5429589A (en) | Hydrogel gauze wound dressing | |
| US20040153040A1 (en) | Multi-layer synthetic dressing with cooling characteristics | |
| JP5020639B2 (en) | Medicinal polyurethane foam | |
| AU651252B2 (en) | Wound dressing comprising polyurethane foam | |
| US6566576B1 (en) | Hydrocolloid foam medical dressings and method of making the same | |
| WO2003092756A1 (en) | Multi-layer synthetic dressing with cooling characteristics | |
| US6099952A (en) | Medical sponge having mucopolysaccharide coating | |
| US20020193723A1 (en) | Compressible foam wound dressing | |
| EP0805663A1 (en) | A dressing having a three-dimensional part and processes for the preparation of such a dressing | |
| EP0489206B1 (en) | Synthetic skin substitutes |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |